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Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm
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Pull KVM fixes from Paolo Bonzini:
 "Bugfixes and improvements to selftests.

  On top of this, Mauro converted the KVM documentation to rst format,
  which was very welcome"

* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (44 commits)
  docs: virt: guest-halt-polling.txt convert to ReST
  docs: kvm: review-checklist.txt: rename to ReST
  docs: kvm: Convert timekeeping.txt to ReST format
  docs: kvm: Convert s390-diag.txt to ReST format
  docs: kvm: Convert ppc-pv.txt to ReST format
  docs: kvm: Convert nested-vmx.txt to ReST format
  docs: kvm: Convert mmu.txt to ReST format
  docs: kvm: Convert locking.txt to ReST format
  docs: kvm: Convert hypercalls.txt to ReST format
  docs: kvm: arm/psci.txt: convert to ReST
  docs: kvm: convert arm/hyp-abi.txt to ReST
  docs: kvm: Convert api.txt to ReST format
  docs: kvm: convert devices/xive.txt to ReST
  docs: kvm: convert devices/xics.txt to ReST
  docs: kvm: convert devices/vm.txt to ReST
  docs: kvm: convert devices/vfio.txt to ReST
  docs: kvm: convert devices/vcpu.txt to ReST
  docs: kvm: convert devices/s390_flic.txt to ReST
  docs: kvm: convert devices/mpic.txt to ReST
  docs: kvm: convert devices/arm-vgit.txt to ReST
  ...
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torvalds committed Feb 16, 2020
2 parents b982df7 + 120881b commit 44024ad
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Original file line number Diff line number Diff line change
@@ -1,9 +1,11 @@
==================
Guest halt polling
==================

The cpuidle_haltpoll driver, with the haltpoll governor, allows
the guest vcpus to poll for a specified amount of time before
halting.

This provides the following benefits to host side polling:

1) The POLL flag is set while polling is performed, which allows
Expand All @@ -29,25 +31,29 @@ Module Parameters
The haltpoll governor has 5 tunable module parameters:

1) guest_halt_poll_ns:

Maximum amount of time, in nanoseconds, that polling is
performed before halting.

Default: 200000

2) guest_halt_poll_shrink:

Division factor used to shrink per-cpu guest_halt_poll_ns when
wakeup event occurs after the global guest_halt_poll_ns.

Default: 2

3) guest_halt_poll_grow:

Multiplication factor used to grow per-cpu guest_halt_poll_ns
when event occurs after per-cpu guest_halt_poll_ns
but before global guest_halt_poll_ns.

Default: 2

4) guest_halt_poll_grow_start:

The per-cpu guest_halt_poll_ns eventually reaches zero
in case of an idle system. This value sets the initial
per-cpu guest_halt_poll_ns when growing. This can
Expand All @@ -66,13 +72,13 @@ high once achieves global guest_halt_poll_ns value).

Default: Y

The module parameters can be set from the debugfs files in:
The module parameters can be set from the debugfs files in::

/sys/module/haltpoll/parameters/

Further Notes
=============

- Care should be taken when setting the guest_halt_poll_ns parameter as a
large value has the potential to drive the cpu usage to 100% on a machine which
would be almost entirely idle otherwise.
large value has the potential to drive the cpu usage to 100% on a machine
which would be almost entirely idle otherwise.
2 changes: 2 additions & 0 deletions Documentation/virt/index.rst
Original file line number Diff line number Diff line change
Expand Up @@ -8,7 +8,9 @@ Linux Virtualization Support
:maxdepth: 2

kvm/index
uml/user_mode_linux
paravirt_ops
guest-halt-polling

.. only:: html and subproject

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